Nanotubes are well known structures exhibiting useful structural, electrical, thermal, and other properties presently of interest in a wide variety of technology areas. Nanotubes may exhibit a variety of intrinsic conductivity states. Fabrication techniques may produce single-wall nanotubes (SW-NT) and/or multiwall nanotubes (MW-NT). Fabrication techniques may also produce nanotubes of varying diameter and/or length. Further, fabrication techniques may produce a variety of chiralities (zigzag, armchair, and chiral). In addition to their composition and perhaps other physical properties, the listed characteristics can influence whether a nanotube is “metallic” (that is, conductive), semiconductive, or insulative.
For some applications, the electrical properties of nanotubes may be of small consequence. However, for other applications, consistent electrical properties between nanotubes may be desired. A difficulty exists in sorting nanotubes according to their electrical or physical properties and/or controlling fabrication methods to produce selected properties. In addition to variance of intrinsic properties between certain types of nanotubes, variance of properties may exist within the same type of nanotube due to defects resulting from a disruption in the pattern of chemical bonds often present in a nanotube. Such defects may potentially change conduction or otherwise have significant implications in some uses for nanotubes.
A variety of techniques are under investigation to sort nanotubes according to their electrical or other properties or to purify nanotube mixtures, removing the byproducts, such as catalysts, particles, etc., of nanotube formation methods. However, conventional purification does not address defective nanotubes and they may remain in purified nanotube mixtures. Even though, techniques exist for identifying the existence and location of nanotube defects, manual sorting remains as the only option for separating nanotubes identified as defective from nanotubes lacking defects. Clearly then, a need exists in the art for better nanotube separation methods.